1. Field of the Invention
The present invention relates to the structure of a development unit for use in an image formation apparatus such as a laser printer, a copier or a facsimile apparatus.
2. Description of the Related Art
Conventionally, a dry developing apparatus, such as disclosed in Japanese Examined Patent Publication No. Hei 4-48232, accomplishes development by supplying developer to a development area on the surface of a photoreceptor drum. According to the disclosed structure of this developing apparatus, a development sleeve is provided in a development case disposed adjacent to the photoreceptor drum. The bore of the development sleeve is provided with a magnetic roller, and a mixture (developer) consisting of toner and magnetic carriers is carried over the outer periphery of the development sleeve. A slit for supplying toner is formed in a partition wall between the development case and a toner supply chamber having a toner agitation member, whereby the case and the chamber communicate with each other through this slit. The agitation member for supplying toner to the inside of the development case is provided in the toner supply chamber, and a lid is provided in a drawable manner in an upper opening formed in the toner supply chamber.
On the other hand, a cartridge lid is provided in a lower opening formed in a toner cartridge, which stores toner for supply purposes, in such a way that it is located at the outside of the lid. The toner cartridge and the toner supply chamber communicate with each other by drawing the lid and the cartridge lid in an integrated fashion while the toner cartridge is attached to the upper opening of the toner supply chamber.
In Japanese Examined Patent Publication No. Hei 4-48232, both the lid of the toner supply chamber and the cartridge chamber of the toner cartridge are fitted in such a way that they are linearly movable in a slidable fashion in the direction orthogonal to the paper as seen in FIG. 1 of that publication, along recessed rails provided on both sides of each of the openings. According to this construction, there are two possible ways to supply toner to the toner supply chamber.
One way is to draw the lid and the cartridge lid in an integrated fashion while the toner cartridge is attached to the toner supply chamber at the first supply of toner, so that both lids are discarded. The attached empty cartridge is held to close the upper opening of the toner supply chamber until the subsequent supply of toner is available. When the subsequent supply of toner is provided, the empty toner cartridge is replaced with a new cartridge, and the new cartridge is attached to the upper opening of the toner supply chamber.
According to this method, it is necessary for the image formation apparatus to be provided with space for holding an empty toner cartridge. This space is so-called "dead space".
Moreover, both the lid and the cartridge lid are discarded. Hence, the upper opening of the toner supply chamber and the lower opening of the empty toner cartridge are temporarily uncovered. Therefore, when the empty toner cartridge is removed, toner housed in both the toner supply chamber and the toner cartridge splashes out, which contaminates the area surrounding the openings.
Another way of supplying toner is to draw the lid and the cartridge lid in an integrated fashion when supplying toner while the toner cartridge is attached to the toner supply chamber. Once the toner contained in the toner cartridge is supplied to the toner supply chamber, the lid and the cartridge lid are returned to their original positions, and each of the openings is closed. In this state, the toner cartridge is removed from the supply chamber together with the cartridge lid.
In this case, the cartridge lid and the lid project in one lateral direction of the supply chamber and the toner cartridge. Toner is attached to each side surface of the cartridge lid and the lid. Hence, even in this case, toner splashes out in the area in the vicinity of the lateral surface. In addition to the cartridge lid and the lid, which both project in an obstructive manner, fingers and clothes of a worker will be soiled by toner, which makes it difficult and unpleasant for the worker to carry out toner supply work.